Medical device for injecting liquid

ABSTRACT

The invention relates to a device for injecting liquid, comprising a piece of tubing on which there is situated at least a first liquid occlusion system. According to the invention, a regulation system ( 4 ) is situated upstream from the first occlusion system, the two systems defining an intermediate segment in which the pressure, in the absence of injection, is greater than the pressure that exists downstream from the first occlusion system so as to direct any leak of liquid from the first occlusion system downstream. The invention is applicable to a pump used for injecting contrast liquid for medical imaging.

The present invention relates to a medical device for injecting liquid.

An application for such a device can lie, for example, with a pump usedfor injecting contrast liquid for medical imaging.

A major problem that results from injecting liquid into patients lies inthe risk of the injection device being contaminated by the patient. Whena liquid is administered to a patient, there is a risk of the injectedliquid flowing back after it has already come into contact with thepatient. Also, in the absence of injection, there still exists a risk ofcontamination by contaminating agents, such as germs, migrating from thepatient to the injection device. As a general rule, this situation makesit essential, when treating a new patient, to change all of the portionsof the device that have already been used.

There exist several devices in the prior art for reducing the risk ofsuch backflow: EP-A-648513 in the name of MEDEX S. A. describes aninjection unit that includes a non-return valve, for example.EP-A-279028 in the names of KABI PHARMACIA GmbH and PFRIMMER-VIGGO GmbHclaims a liquid injection device having a non-return valve characterizedby the fact that the opening pressure can be set to either of twopositions.

Although prior art devices do indeed reduce the risk of backflow, therestill remains the risk of the non-return valve leaking. This risk isparticularly high in the absence of injection.

The present invention thus seeks totally to eliminate any risk ofbackflow. In addition, the present invention also seeks to make itpossible to detect any leak through the safety means that are installedto avoid such backflow, assuming such backflow might indeed take place.

To this end, use is made of a device for injecting liquid, the devicecomprising a piece of tubing on which there is situated at least a firstliquid occlusion system such as a non-return valve. In addition, aregulation system is situated upstream from the first occlusion system,the two systems defining an intermediate segment in which the pressure,in the absence of injection, is greater than the pressure that existsdownstream from the first occlusion system. In this way, any leak ofliquid at the first occlusion system is directed downstream and any leakfrom the intermediate segment can be detected by measuring theassociated pressure drop.

The terms “downstream” and “upstream” mean respectively towards thepatient and in the opposite direction.

By way of example, the regulation system can be a second non-returnvalve or a system for flattening the tubing, such as the wheels of theperistaltic cassette corresponding to patent FR 89/03234 in the name ofMALBEC S. A.

It should be observed that the regulation system cannot be consideredmerely as constituting a safety system in addition to and independent ofthe first occlusion system.

On the contrary, the two systems together constitute an interactiveassembly since the presence of the regulation system makes it possibleto set up, and optionally to maintain, a positive pressure differencebetween the two systems to prevent any leakage of liquid locateddownstream from the first occlusion system from flowing upstream towardsthe intermediate segment.

It should also be observed that the pressure difference between the twosystems is constant in the absence of a leak since the space between thetwo systems is filled with liquid which, like any other liquid, isincompressible.

In order to increase the safety of the device, it is also desirable tohave systems of different kinds. As a result, if one system should fail,the other can nevertheless continue to act, in a manner similar to thatdescribed in the prior art.

Furthermore, when using systems of different kinds, and more preciselysystems characterized by the fact that each of them has a differentopening pressure, it is possible to direct the flow direction of theliquid in the event of a leak or high pressure in the intermediatesegment.

In particular, if the opening pressure of the first occlusion system isless than the opening pressure of the regulation system, any liquidmovement during an interruption of injection will take place downstream,the regulation system closing before the first occlusion system, therebyavoiding any contamination of the portions of the device situatedupstream from the first occlusion system.

Similarly, in the event of high pressure in the intermediate segment,the first occlusion system will be the first to open in the event of aleak, thereby causing the liquid to go downstream from the firstocclusion system and thus preventing any backflow towards theintermediate segment.

It is also possible to envisage that the two opening pressures of theregulation systems are identical, however that can only be envisaged ifthe opening pressure is greater than the pressure that exists downstreamfrom the first occlusion system when there is no injection.

In addition, it is desirable to have an opening pressure for the firstocclusion system which is greater than the maximum pressure that can beset up downstream therefore because of the patient in the absence ofinjection. Also, in the absence of injection, it is necessary for theopening pressure of the first occlusion system to be greater than thepressure of the intermediate segment.

In most cases, in the absence of injection, the pressure that existsdownstream from the first occlusion system corresponds to the venouspressure of the patient.

In another preferred embodiment, it is desirable to provide the tubingwith a disconnection system situated between the two regulation systems.The disconnection system marks the boundary between a downstream tubingfor single use only and an upstream tubing for multiple use.

Thus, when the tubing is contaminated only downstream from thedisconnection system, it is possible to change only that portion of thedevice while reusing the remainder thereof (pumping system, peristalticcassette, reservoir, etc.) with other patients.

The disconnection system is preferably situated as close as possible tothe second regulation device or, which comes to the same thing, as faras possible from the non-return valve. Thus, in the highly improbableevent of contamination propagating upstream, the risk of contaminatingthe zone situated upstream from the disconnection system is minimizedsince the path to be followed to reach the disconnection system is aslong as possible.

In another preferred embodiment, the disconnection system is providedwith occlusion means for the tubing which are activated prior todisconnection, thereby avoiding any risk of liquid being ejected fromthe tubing which is under pressure. Such an automatic closure system isdescribed, for example, in U.S. Pat. Nos. 5,549,566 and 5,533,996 in thenames of ABBOTT LAB and BAXTER INT. INC., respectively.

The above-mentioned occlusion means can also be designed so as to openduring connection.

By way of example, such disconnection systems can be of the “luer-lock”type coupled to a rotary cock system on each of the two connectedsegments. In addition, the connection system between the two pieces canbe of the key and lock type, thus allowing interconnection to take placeonly between two elements that are properly encoded relative to eachother. Such a rotary system makes it possible to open and close the twococks placed on either side of the connection when the key is turned inthe lock, while preventing the two pieces from being disconnected whenthe key is engaged in the position corresponding to the open position ofthe occlusion systems.

The occlusion system situated in the downstream segment can also be anon-return valve, and the system in the upstream segment can be a checkvalve that is open when the two pieces are engaged or, alternatively,the two occlusion systems can be check valves that are open only whenthe two pieces are engaged.

In another preferred embodiment, a pressure sensor is situated on theintermediate segment. As a result, it is possible to detect any pressurevariation in this zone.

When the pressure sensor comes back into contact with the tubing, it isadvantageous to place it between the disconnection system and theregulation system; this configuration has the merit of making itpossible to reuse the same pressure sensor configuration for a pluralityof patients.

In the absence of injection, any pressure drop between the two systemsimplies that a leak is present which, very likely, might have takenplace in the first occlusion system or in the regulation system.

If the leak has taken place in the first occlusion system, thencontamination can propagate into the tubing for multiple use.

If the leak has taken place in the regulation system, then contaminationhas not necessarily propagated into the tubing for multiple use, but therisk of that happening has nevertheless been increased since any leak atthe first occlusion system gives rise to a drop in pressure in theintermediate segment, thus eliminating the effect of the means installedin the context of the present invention.

In order to mitigate the two above-described situations, it isadvantageous to associate an alarm 102 with the pressure sensor placedon the intermediate segment. Furthermore, in even more advantageousmanner, liquid injection can be triggered as to reestablish the initialpressure when the alarm is activated.

It should also be observed that maintaining a high pressure in theintermediate segment, close to the pressure for opening the firstocclusion system, can serve to favor leakage at said first occlusionsystem.

To this end, means are provided to reduce the pressure in theintermediate segment. These means can be constituted by an intermediatechamber of adjustable volume. By way of example, the volume of theintermediate chamber can be adjusted by a piston. Thus, the pressurewhich exists in the intermediate segment can be selected so as to begreater than the pressure downstream from the first occlusion system andfar enough away from the opening pressure of said first occlusion systemto make full use of the sealing characteristics of said first occlusionsystem. Another means enabling said pressure to be lowered below theopening threshold of the first occlusion system consists in selecting aregulation system whose opening can be adjusted in such a manner as tolower the pressure of the intermediate segment to a predetermined value.

Although adjusting the pressure in the intermediate segment considerablyreduces any risk of contamination, it is still possible after an alarmis triggered to change the portions that might have been contaminated,for example portions such as the peristaltic cassette. Under suchcircumstances, it is advantageous for this purpose to provide a seconddisconnection system upstream from the regulation system.

Optionally, a second pressure sensor can be placed on the segment oftubing which is to be found downstream from the first occlusion system,thus making it possible, for example, to detect any excess pressurecompared with the pressure in the intermediate segment.

It is also possible to provide the device with a system for measuringthe pressure difference as measured by the two sensors, thus having theadvantage of determining the risk of backflow more directly. An alarmcan be triggered when the pressures situated upstream and downstream ofthe non-return valve are tending to become equal.

The medical device of the invention can also be designed in such amanner as to deactivate the alarm when the single-use tubing isdisconnected.

The medical device of the invention may advantageously include a syringedriver 100. A pressure sensor 108 can be placed on the distal end of thepiston 106 of the syringe driver.

Assuming that syringe driver 100 is used, it is possible to consider thesyringe 104 itself as being an integral portion of the intermediatesegment, and the syringe itself can form the regulation system. Inaddition, under these circumstances, the syringe 104 can also act as asystem for regulating the intermediate chamber so as to enable thepressure in the intermediate chamber to be adjusted.

The medical device of the invention can be used with any type of liquid,and in particular it can be used for injecting contrast liquids.

The invention is described below by way of an example and with referenceto the accompanying drawings, in which:

FIG. 1A is a diagram showing a preferred embodiment of the invention;

FIG. 1B is a diagram showing an alternative embodiment of the invention;

FIGS. 2A to 2I show various steps in the operation of a preferreddisconnection system in its first use;

FIGS. 2′A and 2′B correspond to the steps of FIGS. 2A and 2B when thedisconnection system is used on subsequent occasions;

FIG. 3 is a longitudinal section of a preferred embodiment of anon-return valve; and

FIGS. 4 and 5 are perspective views of the disconnection system of FIGS.2A to 2I, 2′A, and 2′B, respectively before and after connection to aliquid injection device, downstream from a peristaltic cassette.

The liquid injection device in one embodiment (FIG. 1A) is constitutedessentially by a piece of tubing, a reservoir 1, a pump system 2 anintermediate chamber 3 of variable volume, a regulation system 4 whichmay include the wheels of a peristaltic pump, and a non-return valve 7.A disconnection system 6 is situated upstream from the non-return valve7, between said valve and the regulation system. Pressure sensors 5 and8 are situated downstream and upstream from the non-return valve.

In the absence of injection, i.e. when the pump is deactivated, constantpressure exists between the non-return valve and the second regulationsystem. The constant pressure is lower than the opening pressure of thenon-return valve.

If the non-return valve is defective, backflow of liquid towards thepump is prevented by the flow of liquid associated with the pressurethat exists in the intermediate segment, with this pressure in theintermediate segment being due to the presence of the peristalticcassette which, in the absence of injection, is very effective atoccluding the tubing. The opening pressure of the occlusion systemconstituted by the wheels of the peristaltic cassette is greater than 8bars, whereas the opening pressure of the first occlusion system isequal to 0.5 bars.

The present invention is naturally not limited solely to the exampledescribed above, with all configurations of the description also beingincluded.

Thus, and preferably, the first occlusion system, or the regulationsystem, or both of them, are of the automatic clamp type. It is alsopossible to use a fourth occlusion device, preferably located downstreamfrom the disconnection system, which device is activated in the event ofan alarm being triggered.

The device of the present invention can also include a pressure sensormeasuring the pressure of the liquid in a length of tubing situatedupstream from the intermediate segment.

With reference to FIG. 2A, a preferred disconnection system 6 comprisesan upstream piece 10 having an intermediate chamber 12 of adjustablevolume, and a downstream piece 14 provided with the non-return valve 7and capable of co-operating in reversible manner with the upstream piece10 so as to form a sealed link.

The upstream piece 10 is constituted by a hollow tubular body 15 that isopen at both ends, defining an inside volume that is split into two byan open internal radial wall 16 placed between an injection chamber 18and the intermediate chamber 12 of adjustable volume, constituting adecompression chamber as explained below.

The intermediate chamber 12 contains a pre-split resilient septum 20whose diameter is substantially equal to the inside diameter of theintermediate chamber 12 so as to form a piston that is movable intranslation.

The downstream piece 14 comprises a hollow circulary-symmetrical body 22that is extended at its two open ends by respective hollow rods. Thebody 22 surrounds an inside volume which is split in two by an openradial wall 24 placed between a first chamber 26 in which the non-returnvalve 7 is formed, and a second chamber 28 facing towards the patient.

The hollow rod 30 adjacent to the first chamber 26 has a free end whoseshape includes a frustoconical portion, and it is designed to be placedinside the intermediate chamber 12 by passing through the septum 20 andthe opening of the wall 16. The hollow rod 30 has an outer annularcollar 32 that comes into abutment against the septum 20 so as to driveit in translation inside the intermediate chamber 12 (FIG. 2B), theseptum 20 coming into abutment against the wall 16 when the rod 30 ispushed home fully into the piece 10, the tubular body 15 then cominginto abutment against the body 22 (FIG. 2C).

Locking means are also provided between the pieces 10 and 14, e.g. inthe form of a resilient locking tab situated outside the body 15 andhaving a free end that snap-fastens against a shoulder or a groove inthe outside surface of the body 22. Such a tab 34 is shown in FIG. 2B inassociation with a shoulder that faces in the opposite direction to thehollow rod 30 when the bodies 15 and 22 are in abutment.

A non-return valve 7 shown is formed by a plug 38 that is capable ofbeing compressed (collapsing) radially enabling it to be bypassed by theliquid when the pressure of the liquid upstream from the plug 38 isgreater than or equal to the opening pressure of the non-return valve 7.

This type of plug is preferably as described in U.S. Pat. No. 4,929,230,i.e. a plug made of resilient material of longitudinal section that canbe seen in FIGS. 2A to 2I and 2′A, 2′B, and even more clearly in FIG. 3.The plug 38 has a first end directed towards the second chamber 28 withsealing means 46 that cooperate with the inside surface of the secondchamber 28, a second end directed towards the hollow rod 30, at leastone frustoconical surface portion 40 between the sealing means and thesecond end, and a cavity 42 extending inside said plug said first endand over a depth that is greater than the distance between the sealingmeans and the free edge of the first end. This plug 38 also has aretractable wall 44 between at least a portion of said frustoconicalsurface 40 and said cavity 42, said retractable wall 44 extending atleast from the end of said cavity 42 as far as first end and retractinginto said cavity 42 when the radial resultant of the pressure exerted onsaid frustoconical surface 40 by said liquid is greater than the sum ofthe radial compression strength of the retractable wall 44 plus theinternal pressure of the cavity 42.

This type of plug 38 can also be placed in the tubing as a secondocclusion system 4.

In a preferred embodiment, the opening pressure of the non-return valve7 is greater than its closing pressure. By way of example, the plug 38can be shaped so that it is compressed, thereby opening the valve 7,starting from a pressure of 1.2 bars for the liquid in the hollow rod30, the retractable wall 44 returning to its initial shape and thusclosing the valve 7 when the pressure of the liquid in the hollow rod isequal to or less than 0.8 bars.

Prior to any injection (FIGS. 2A and 2B) the pieces 10 and 14 of theconnection system 6 are empty of liquid, i.e. they have atmosphericpressure (Pa) within them.

In general, throughout the description below, when said atmosphericpressure Pa is not mentioned, it should be assumed that it is to beadded to the liquid pressure mentioned.

After the pieces 10 and 14 have been connected together, the injectiondevice is primed (FIG. 2C) by sending liquid at a pressure greater than1.2 bars (P>1.2) into the injection chamber 18. This liquid passes alongthe hollow rod 30, the septum 20 closing the intermediate chamber 12 insealed manner, which chamber presents substantially zero volume incommunication with the injection chamber 18. Because of this pressure of1.2 bars which is greater than the opening pressure of the valve 7, thevalve is opened and the liquid can pass through the first chamber 26 andleave the second chamber 28 in communication with the outside (Pa).

The following step (FIG. 2D) consists in stopping the delivery of liquidunder pressure, the injection chamber 18 then being filled with a liquidat a pressure of about 0.8 bars (P0.8) causing the valve 7 to close byvirtue of the retractable wall 44 returning to its initial position.

Once the valve 7 has closed, the injection device is connected to thepatient so that the patient's venous pressure which is close to 0.2 bars(P0.2) corresponds substantially to the pressure of the liquid in thesecond chamber 28.

During injection (FIG. 2E), the pressure of the liquid in thedisconnection system 6 is greater than 1.2 bars (P8), thereby holdingthe valve 7 open.

Once injection is over (FIG. 2F) the situation of the disconnectionsystem 6 is identical to its situation (FIG. 2D) preceding the injectionstep (FIG. 2E).

When the patient is disconnected (FIG. 2G) from the injection device,the valve 7 remains closed, since the pressure of the liquid in thesecond chamber 28 is substantially zero (ignoring atmospheric pressure)and the pressure of the liquid in the injection chamber 18 issubstantially of the order of 0.8 bars.

Thus, when the pieces 10 and 14 of the disconnection system 6 are movedapart (FIG. 2H), as the hollow rod 30 is withdrawn and the collar 32moves away from the wall 16, the septum 20 also moves away from the wall16 since the liquid pressure in the injection chamber 18 is greater thanthe pressure inside the second chamber 28.

The volume of the chambers 12 and 18 is designed to enable the septum 20to move far enough away from the wall 16 to enable the pressure in thechambers 12 and 18 to drop to the level of atmospheric pressure so thatthe two pieces 10 and 14 can be separated (FIG. 2I) without any risk ofliquid flowing out from the second chamber 28 or from the hollow rod 30.It will be understood that the internal volume of said upstream piece 18is shaped so as to make it possible to obtain liquid pressure in thedisconnection system 6 which is less than or equal to atmosphericpressure prior to said upstream and downstream pieces 10 and 14 beingseparated fully.

Because of this disconnection system, the plug 38 prevents the liquidthat has filled the second chamber 28 and that has been in communicationwith the tubing connected to the patient from flowing back upstream. Inaddition, any outflow of liquid is avoided when the pieces 10 and 14 aredisconnected.

When the injection device is used on a new patient, a new downstreampiece 14′ is used which is connected to the upstream piece 10 that hasalready been used on a preceding patient (FIGS. 2′A and 2′B). Thesubsequent steps in performing injection are identical to the stepsillustrated by FIGS. 2C to 2I as already described.

What is claimed is:
 1. A device for injecting liquid under pressure to apatient, the device comprising: means for pumping the liquid, a lengthof tubing extending from the pumping means to the patient; a regulationsystem located on the length of tubing; a first occlusion system locatedon the length of tubing downstream of the regulation system, the firstocclusion system and the regulation system defining an intermediatesegment having an intermediate pressure, a segment of tubing downstreamof the first occlusion system having a downstream pressure, wherein theintermediate pressure, in the absence of injection to the patient, isgreater than the downstream pressure to direct leakage of liquid fromthe first occlusion system downstream toward the patient; a firstpressure sensor connected to the intermediate segment which measures anydrop in the intermediate pressure in the absence of injection to thepatient to detect leakage from the intermediate segment, the firstpressure sensor having an output indicative of leakage from theintermediate segment, said output being operative in the absence ofinjection to the patient; means responsive to the output of the firstpressure sensor for assisting in prevention of contamination ofcomponents upstream of the first occlusion system; and a disconnectionsystem situated on the intermediate segment, said disconnection systemcomprising a boundary between a piece of tubing downstream therefrom forsingle use and a piece of tubing upstream therefrom for multiple use,wherein said disconnection system further comprises means for occludingat least one piece of the tubing that is activated prior todisconnection.
 2. The device according to claim 1, wherein saiddisconnection system comprises two mutually mated pieces which enablethe occlusion means to be activated or deactivated only if the mating ofone piece complies with that of the other.
 3. The device according toclaim 2, wherein said occlusion means includes a septum mounted to atleast one of the two pieces, said septum being structured to openautomatically when the two pieces are engaged in a sealed manner.
 4. Thedevice according to claim 3, wherein the septum is structured to closein a sealed manner when the two pieces are disengaged.
 5. A device forinjecting liquid under pressure to a patient, the device comprising:means for pumping the liquid; a length of tubing extending from thepumping means to the patient; a regulation system located on the lengthof tubing; a first occlusion system located on the length of tubingdownstream of the regulation system the first occlusion system and theregulation system defining an intermediate segment having anintermediate pressure, a segment of tubing downstream of the firstocclusion system having a downstream pressure wherein the intermediatepressure, in the absence of injection to the patient is greater than thedownstream pressure to direct leakage of liquid from the first occlusionsystem downstream toward the patient; a first pressure sensor connectedto the intermediate segment which measures any drop in the intermediatepressure in the absence of injection to the patient to detect leakagefrom the intermediate segment, the first pressure sensor having anoutput indicative of leakage from the intermediate segment, said outputbeing operative in the absence of injection to the patient; and meansresponsive to the output of the first pressure sensor for assisting inprevention of contamination of components upstream of the firstocclusion system, wherein the means for assisting includes the means forpumping which is activated in response to the output of the firstpressure sensor indicative of leakage from the intermediate segment soas to maintain the intermediate pressure in said intermediate segment atleast at a predetermined threshold.
 6. A device for injecting liquidunder pressure to a patient, the device comprising: means for pumpingthe liquid; a length of tubing extending from the pumping means to thepatient; a regulation system located on the length of tubing; a firstocclusion system located on the length of tubing downstream of theregulation system, the first occlusion system and the regulation systemdefining an intermediate segment having an intermediate pressure, asegment of tubing downstream of the first occlusion system having adownstream pressure, wherein the intermediate pressure, in the absenceof injection to the patient, is greater than the downstream pressure todirect leakage of liquid from the first occlusion system downstreamtoward the patient; a first pressure sensor connected to theintermediate segment which measures any drop in the intermediatepressure in the absence of injection to the patient to detect leakagefrom the intermediate segment, the first pressure sensor having anoutput indicative of leakage from the intermediate segment, said outputbeing operative in the absence of injection to the patient; and meansresponsive to the output of the first pressure sensor for assisting inprevention of contamination of components upstream of the firstocclusion system, wherein the means for assisting includes means formodifying the intermediate pressure of said intermediate segment in theabsence of injection to the patient so as to obtain an intermediatepressure which lies between the downstream pressure and the openingpressure of the first occlusion system.
 7. The device according to claim6, wherein said means for modifying the intermediate pressure isresponsive to the output of the first pressure sensor and activates themeans for pumping.
 8. The device according to claim 6, wherein saidmeans for modifying includes a syringe driver and a syringe, the syringeforming an integral portion of the intermediate segment.
 9. The deviceaccording to claim 8, wherein the first pressure sensor is situated at adistal end of a piston of the syringe driver which moves a piston of thesyringe.
 10. The device according to claim 8, wherein the means forpumping includes the syringe and the syringe driver of said means formodifying the intermediate pressure of the intermediate segment.
 11. Thedevice according to claim 6, wherein said means for pumping includes apump.
 12. The device according to claim 11, wherein the means formodifying includes a syringe which forms an integral portion of theintermediate segment, a piston of the syringe constructed to adjust avolume of said intermediate chamber.
 13. The device according to claim11, wherein the means for modifying includes the pump.
 14. The deviceaccording to claim 6, wherein the means for modifying includes a pumpseparate from the means for pumping.
 15. A device for injecting liquidunder pressure to a patient, the device comprising: means for pumpingthe liquid; a length of tubing extending from the pumping means to thepatient; a regulation system located on the length of tubing; a firstocclusion system located on the length of tubing downstream of theregulation system, the first occlusion system and the regulation systemdefining an intermediate segment having an intermediate pressure, asegment of tubing downstream of the first occlusion system having adownstream pressure, wherein the intermediate pressure, in the absenceof injection to the patient, is greater than the downstream pressure todirect leakage of liquid from the first occlusion system downstreamtoward the patient; a first pressure sensor connected to theintermediate segment which measures any drop in the intermediatepressure in the absence of injection to the patient to detect leakagefrom the intermediate segment, the first pressure sensor having anoutput indicative of leakage from the intermediate segment, said outputbeing operative in the absence of injection to the patient; meansresponsive to the output of the first pressure sensor for assisting inprevention of contamination of components upstream of the firstocclusion system; and a disconnection system situated on theintermediate segment, said disconnection system comprising a boundarybetween a piece of tubing downstream therefrom for single use and apiece of tubing upstream therefrom for multiple use, wherein saidupstream piece and said downstream piece are capable of co-operating inreleasable manner so as to form a leakproof link, said upstream piecehaving an intermediate chamber having an internal volume that isadjustable by a moving piston.
 16. The device according to claim 15,wherein the piston is structured to increase the internal volume of theupstream piece to obtain a pressure in the upstream piece less than orequal to atmospheric pressure, prior to the upstream piece anddownstream piece being fully released.
 17. The device according to claim16, wherein the means for pumping includes a syringe and the piston is aportion of the syringe.
 18. The device according to claim 16, whereinthe piston is a septum mounted to the intermediate chamber of theupstream piece.
 19. The device according to claim 15, wherein theintermediate chamber is in communication with the intermediate segment.20. The device according to claim 15, wherein the means for pumpingincludes a syringe.
 21. The device according to claim 20, wherein theintermediate chamber includes a volume of the syringe.
 22. A device forinjecting liquid under pressure to a patient, the device comprising:means for pumping the liquid; a length of tubing extending from thepumping means to the patient; a regulation system located on the lengthof tubing; a first occlusion system located on the length of tubingdownstream of the regulation system, the first occlusion system and theregulation system defining an intermediate segment having anintermediate pressure, a segment of tubing downstream of the firstocclusion system having a downstream pressure, wherein the intermediatepressure, in the absence of injection to the patient, is greater thanthe downstream pressure to direct leakage of liquid from the firstocclusion system downstream toward the patient; a first pressure sensorconnected to the intermediate segment which measures any drop in theintermediate pressure in the absence of injection to the patient todetect leakage from the intermediate segment, the first pressure sensorhaving an output indicative of leakage from the intermediate segment,said output being operative in the absence of injection to the patient;means responsive to the output of the first pressure sensor forassisting in prevention of contamination of components upstream of thefirst occlusion system; a second pressure sensor situated on a patienttubing segment located downstream from the first occlusion system; and ameasurement system responsive to the output of the first pressure sensorand an output of the second pressure sensor, the measurement systemstructured to measure a difference in pressure between the pressure inthe intermediate segment and the pressure in the patient tubing segmentdownstream from the first occlusion system in the absence of injectionto the patient, wherein the means for assisting includes the means forpumping, wherein in the absence of injection to the patient, the meansfor pumping is activated in response to measurement of the pressure inthe intermediate segment being approximately equal to or less than thepressure in the patient tubing segment downstream from the firstocclusion system, so as to maintain the intermediate pressure in theintermediate segment above the pressure in the patient tubing.
 23. Adevice for injecting liquid under pressure to a patient, the devicecomprising: means for pumping the liquid; a length of tubing extendingfrom the pumping means to the patient; a regulation system located onthe length of tubing and having a second opening pressure; a firstocclusion system located on the length of tubing downstream of theregulation system and having a first opening pressure, the first openingpressure being lower than the second opening pressure; and wherein thefirst occlusion system and the regulation system define an intermediatesegment having an intermediate pressure, a segment of tubing downstreamof the first occlusion system having a downstream pressure, wherein theintermediate pressure, in the absence of injection to the patient, isgreater than the downstream pressure to direct leakage of liquid fromthe first occlusion system downstream toward the patient.
 24. The deviceaccording to claim 23, wherein said first occlusion system includes anon-return valve.
 25. The device according to claim 24, wherein saidnon-return valve comprises a plug capable of being compressed radiallyso as to allow liquid to bypass it in the event of the pressure of theliquid upstream fro said plug being greater than or equal to the firstopening pressure of said non-return valve.
 26. The device according toclaim 24, wherein said first opening pressure is greater than a closingpressure of the non-return valve.
 27. The device according to claim 23,wherein said regulation system includes a second occlusion system. 28.The device according to claim 27, wherein said second occlusion systemincludes a system involving flattening of the tubing.
 29. The deviceaccording to claim 28, wherein said means for pumping includes aperistaltic cassette pump and wherein said system for flattening thetubing includes the wheels of the peristaltic cassette pump.
 30. Thedevice according to claim 27, wherein said second occlusion systemincludes a non-return valve.
 31. The device according to claim 30,wherein said non-return valve comprises a plug capable of beingcompressed radially so as to enable it to be bypassed by the liquid whenthe pressure of the liquid upstream from the plug is greater than orequal to the first opening pressure.
 32. The device according to claim27, wherein said second occlusion system includes an automatic clamp.33. The device according to claim 27, wherein said second occlusionsystem includes a system which compresses the tubing.
 34. The deviceaccording to claim 23, wherein the first opening pressure of the firstocclusion system is greater than the intermediate pressure that existsin the intermediate segment in the absence of injection to the patient.35. The device according to claim 23, further comprising a disconnectionsystem situated on the intermediate segment, said disconnection systemcomprising a boundary between a piece of tubing downstream therefrom forsingle use and a piece of tubing upstream therefrom for multiple use.36. The device according to claim 35, wherein said disconnection systemcomprises means for occluding at least one piece of the tubing that isstructured to be activated prior to disconnection.
 37. The deviceaccording to claim 36, wherein said disconnection system comprises twomutually mated pieces which enable the occlusion means to be activatedor deactivated only if the mating of one piece complies with that of theother.
 38. The device according to claim 37, wherein said occlusionmeans includes a septum mounted to at least one of the two pieces, saidseptum being structured to open automatically when the two pieces areengaged in a sealed manner.
 39. The device according to claim 38,wherein the septum is structured to close in a sealed manner when thetwo pieces are disengaged.
 40. The device according to claim 35, furthercomprising a first pressure sensor located on the intermediate segmentwhich measures a drop in the intermediate pressure in the absence ofinjection to the patient to detect leakage from the intermediatesegment, the first pressure sensor contacting a multiple use piece ofsaid tubing.
 41. The device according to claim 35, wherein said upstreampiece and said downstream piece are capable of co-operating inreleasable manner so as to form a leakproof link, said upstream piecehaving an intermediate chamber having an internal volume that isadjustable by a moving piston.
 42. The device according to claim 41,wherein the piston is structured to increase the internal volume of theupstream piece to obtain a pressure in the upstream piece less than orequal to atmospheric pressure, prior to the upstream piece and thedownstream piece being fully released.
 43. The device according to claim42, wherein the means for pumping includes a syringe and the piston is aportion of the syringe.
 44. The device according to claim 42, whereinthe piston is a septum mounted to the intermediate chamber of theupstream piece.
 45. The device according to claim 41, wherein theintermediate chamber is in communication with the intermediate segment.46. The device according to claim 41, wherein the means for pumpingincludes a syringe.
 47. The device according to claim 46, wherein theintermediate chamber includes a volume of the syringe.
 48. The deviceaccording to claim 23, further comprising a first pressure sensorlocated on the intermediate segment which measures a drop in theintermediate pressure in the absence of injection to the patient todetect leakage from the intermediate segment, the first pressure sensorhaving an output indicative of leakage from the intermediate segment.49. The device according to claim 48, further comprising a secondpressure sensor situated on a patient tubing segment located downstreamfrom the first occlusion system.
 50. The device according to claim 49,further comprising a measurement system responsive to the output of thefirst pressure sensor and an output of the second pressure sensor, themeasurement system structured to measure a difference in pressurebetween the pressure in the intermediate segment and the pressure in thepatient tubing segment downstream from the first occlusion system in theabsence of injection to the patient.
 51. The device according to claim50, further comprising an alarm, wherein in the absence of injection tothe patient, the alarm is triggered if the pressure in the intermediatesegment is approximately equal to or less than the pressure in thepatient tubing segment downstream from the first occlusion system. 52.The device according to claim 50, wherein in the absence of injection tothe patient, the means for pumping is activated in response tomeasurement of the pressure in the intermediate segment beingapproximately equal to or less than the pressure in the patient tubingsegment downstream from the first occlusion system, so as to maintainthe intermediate pressure in the intermediate segment above the pressurein the patient tubing.
 53. The device according to claim 48, furthercomprising an alarm responsive to the output of the first pressuresensor, wherein in the absence of injection to the patient, the alarm istriggered if the intermediate pressure in the intermediate segmentdecreases.
 54. The device according to claim 53, further comprising asecond disconnection system which is situated upstream from theregulation system, the second disconnection system enabling theintermediate segment to be changed in the event of the alarm occurringthat is associated with a risk of contamination.
 55. The deviceaccording to claim 53, wherein the alarm is triggered if theintermediate pressure drops beneath a predetermined value.
 56. Thedevice according to claim 48, wherein the means for pumping is activatedin response to the output of the first pressure sensor indicative ofleakage from the intermediate segment so as to maintain the intermediatepressure in said intermediate segment at least at a predeterminedthreshold.
 57. The device according to claim 48, further comprising analarm responsive to the output of the first pressure sensor, the alarmbeing triggered if the intermediate pressure in the intermediate segmentincreases or if the intermediate pressure rises above a predeterminedvalue.
 58. The device according to claim 48, further comprising meansfor modifying the intermediate pressure of said intermediate segment inthe absence of injection to the patient so as to obtain an intermediatepressure which lies between the downstream pressure and the openingpressure of the first occlusion system.
 59. The device according toclaim 58, wherein said means for modifying the intermediate pressure isresponsive to the output of the first pressure sensor and activates themeans for pumping.
 60. The device according to claim 58, wherein saidmeans for modifying includes a syringe driver and a syringe, the syringeforming an integral portion of the intermediate segment.
 61. The deviceaccording to claim 60, wherein the first pressure sensor is situated ata distal end of a piston of the syringe driver which moves a piston ofthe syringe.
 62. The device according to claim 60, wherein the means forpumping includes the syringe and the syringe driver of said means formodifying the intermediate pressure of the intermediate segment.
 63. Thedevice according to claim 58, wherein said means for pumping includes apump.
 64. The device according to claim 63, wherein the means formodifying includes a syringe which forms an integral portion of theintermediate segment, a piston of the syringe constructed to adjust avolume of said intermediate chamber.
 65. The device according to claim63, wherein the means for modifying includes the pump.
 66. The deviceaccording to claim 48, further comprising a second pressure sensormeasuring the pressure of the liquid in a length of the tubing situatedupstream from the intermediate segment.
 67. The device according toclaim 23, wherein the liquid under pressure includes contrast media. 68.The device according to claim 23, wherein the means for pumping includesa pump.
 69. The device according to claim 68, wherein the pump includesa peristaltic cassette pump.
 70. The device according to claim 23,wherein the means for pumping includes a syringe.
 71. The deviceaccording to claim 23, wherein said first occlusion system includes anautomatic clamp.
 72. The device according to claim 23, wherein theregulation system is located downstream from the means for pumping. 73.The device according to claim 23 wherein the regulation system includesat least an element of the means for pumping.
 74. The device accordingto claim 73, wherein the means for pumping includes a syringe and theregulation system includes a piston of the syringe.